Biosupramolecular complexes of amphiphilic photosensitizers with human serum albumin and cucurbit[7]uril as carriers for photodynamic therapy

Binding of toluidine blue-myristic acid derivative to cucurbit[7]uril and human serum albumin: computational and biophysical insights towards a biosupramolecular assembly

“…6A, the carboxylate group was located outside the macrocycle due to the repulsion with the electron-dense carbonyl groups at the entry portals, while the previously reported TBOC14 derivative with a neutral alkyl chain showed two conformations, being the binding of the “tail” very favorable. 42 The main energy contribution to the system came from the insertion of the aromatic system into the CB[7] cavity, favoring van der Waals and desolvation interactions. There was also a coulombic contribution given by the interaction between the positive imine group and the carbonyl groups of CB[7], as previously reported.…”

“…The fact that the “myristate” portion of the molecule was not included in the cavity of CB[7] but rather the TBO core, is in agreement with the strong increase in fluorescence intensity for the TBOMyr derivative compared to TBOC14. 42…”

“…We and others have reported the interactions between PS, CB[ n ]s and HSA, which in some cases lead to interesting ternary complexes. 20,34–42 Research in the literature has focused on available dyes, while the design and synthesis of ditopic PS that could bind strongly to both CB[7] and HSA simultaneously has not been explored in detail. Recently, we studied the photophysics and supramolecular interactions of TBO amphiphilic derivatives bearing different length alkyl chains (TBOC6 and TBOC14) with CB[7] and HSA, and their effect on phototoxicity in cultured tumoral cells.…”

“…Recently, we studied the photophysics and supramolecular interactions of TBO amphiphilic derivatives bearing different length alkyl chains (TBOC6 and TBOC14) with CB[7] and HSA, and their effect on phototoxicity in cultured tumoral cells. 42,43 In the present work, we investigated the binding of a new TBO derivative, namely TBOMyr (Chart 1D), containing a 14-carbon atom chain and a terminal carboxylate group, mimicking the structure of Myr. This is relevant since our previous studies showed the favorable inclusion of the hydrophobic tail of the compounds in CB[7], which was not desired, leading to mild effect on their photophysics/photochemistry.…”

“…This is relevant since our previous studies showed the favorable inclusion of the hydrophobic tail of the compounds in CB[7], which was not desired, leading to mild effect on their photophysics/photochemistry. 42 With the TBOMyr derivative, we aim to selectively encapsulate the photosensitive portion of the derivate to enhance its photophysical properties, while the hydrophobic character of the aliphatic chain and the addition of the carboxylate group could enhance the association of the derivate to HSA given the characteristics of the protein's binding pockets.…”